Vacuum sweeping machines known from the prior art, such as DE 197 15 435 C2, have a chassis by means of which the machine can be moved over a surface to be cleaned, such as pavements, streets, public squares and the like. Mounted on the chassis is a driven sweeping device having brushes that move over the surface. Normally, such a sweeping device is formed as a sweeping roller which extends transversely in relation to the direction of travel parallel in relation to the surface and which is driven in rotation. The sweeping roller in this case is surrounded by a sweeping-roller housing, which is connected to a suction extraction device in order to suck up dust swirled up by the sweeping roller.
Frequently, in addition to the sweeping roller that is mounted on the chassis and extends over the width thereof and transversely in relation to the direction of travel, such sweeping machines are also provided with a side broom, which is mounted laterally on the chassis and by means of which peripheral regions of the surfaces to be cleaned that are not covered by the sweeping roller, for example curbstones, can be cleaned.
In order to reduce dust emissions at the side broom of sweeping machines, water spray jets or enclosures are additionally used. Spray jets are used predominantly in the cleaning of exterior spaces, whereas in the cleaning of interior spaces there is often the requirement that the surface to be cleaned is to remain dry. Enclosures are therefore used in some cases where requirements relating to air quality in enclosed spaces are more stringent. The present invention therefore relates to dry-operation, mechanical pick-up sweeping machines having a side broom.
Side-broom enclosures alone have only a slight effect on the reduction of dust emissions of a side broom. In order to operate them effectively, the air has to be sucked out of the enclosure, so that a negative pressure is created inside the enclosure. The dust-laden air must then be cleaned by means of a dust separator. In order to prevent the escape of dust, the suction extraction system in this case must deliver a sufficiently high volumetric flow rate of air from the outside to the inside, through the side-broom enclosure.
There are various technical ways of meeting this air volumetric flow rate requirement for the side-broom suction extraction system, which is in addition to the suction extraction system in the case of the sweeping roller. On the one hand, it is possible to install an additional blower, which sucks up the dust-laden air out of the side-broom enclosure, solely for the purpose of side-broom suction extraction, and cleans this air by means of an additional dust separator provided for this purpose. This solution requires a large amount of structural space, creates additional acquisition and operating costs and, for the operator, increases the maintenance work.
On the other hand, it is possible to use the already existing suction extraction device and the fine filter for dust-free operation of the sweeping roller and also for the side-broom enclosure. For this purpose, the sweeping-roller housing is connected to the side-broom enclosure via a suction line. The blower must then be dimensioned for the volumetric flow rate demand of both the sweeping-roller housing and the side-broom enclosure.
However, if such a machine having a larger-dimensioned blower is operated without side-broom suction extraction, then, unless additional modifications are made to the machine, the fine filter becomes loaded by an increased volumetric flow rate of dust-laden air. This leads to more rapid fouling, and consequently to shorter cleaning intervals, which result in more frequent interruption of the sweeping operation.